Antidepressants Flashcards
What are the main types of antidepressants?
- Selective serotonin reuptake inhibitors (SSRIs)
- Serotonin and noradrenaline reuptake inhibitors (SNRIs)
- Tricyclic antidepressants (TCAs)
- Others (mirtazapine and vortioxetine)
How do SSRIs work?
Block the reuptake of serotonin by the Presynpatic membrane on the axon terminal
Causes more serotonin in the synapses in the CNS, boosting communication between neurones
Can lead to down-regulation of post-synaptic serotonin receptors
How do SNRIs work?
Blocking the reuptake of serotonin and NorAd by the presynaptic membrane
More serotonin and NorAd in synapses in the CNS
How do Tricyclic antidepressants work?
Block reuptake of serotonin and NorAd by presynaptic membrane
Block ACh and histamine receptors giving them anticholinergic and sedative side effects
What are the common ACh (muscarinic) effects?
- Dry mouth
- Thirst
- Difficulty urinating
- Urinary retention
- Dry skin
- Hot and flushed skin
What are the common Histamine effects?
- Dry mouth
- Drowsiness
- Dizziness
- Nausea and vomiting
What are the common Adrenaline/NorAd effects?
- Sweating
- Tremor
- Headaches
- Nausea
- Dizziness
What are some examples of SSRIs?
Sertraline
Citalopram
Escitalopram
Fluoxetine
Paroxetine
Outline sertraline
Anti-anxiety effects
Considered one of the safest in patients with heart disease
Higher rate of diarrhoea
Outline citalopram
Can prolong QT interval (dose dependent)
QT prolongation can cause torsades de pointes
Along with escitalopram, least safe SSRI in patients with heart disease (still safer than TCAs)
Why is fluoxetine the first-line choice in children and adolescents?
Long half-life of 4-7 days
Remains active in the body long after stopping
What can paroxetine cause?
Weight gain
Discontinuation symptoms
What are the key side effects of SSRIs?
GI symptoms
Headaches
Sexual dysfunction
Hyponatraemia
Anxiety or agitation
Increased suicidal thoughts, suicide risk, self-harm
Increased bleeding risk (especially with anticoags or NSAIDs)
What are some examples of SNRIs?
Duloxetine
Venlafaxine
What are some side effects of SNRIs?
Similar to SSRIs
Increased blood pressure
Contraindicated in uncontrolled hypertension
When is venlafaxine used?
Inadequate response to other antidepressants
- More likely to cause discontinuation symptoms when stopped
- Increased risk of death from O.D
- Must measure blood pressure
What are some examples of TCAs?
Amitriptyline
Nortriptyline
Used at low dose for neuropathic pain (this dose is too low to treat depression)
What are TCAs known to cause?
Arrhythmias e.g.
- Tachycardia
- Prolonged QT interval
- Bundle branch block
- Dry mouth
- Urinary retention
What should patients be warned about when taking TCAs?
Blurred vision espeically if they drive or operate heavy machinery
Due to antimuscarinic properties of TCAs
Why are TCAs taken at night?
Due to its anticholinergic effects it also causes sedation